In aqueous paints, such as paints that use acrylic-based latices, a pH adjustment is generally necessary in order to stabilize the latex. This adjustment is called neutralization. Furthermore, when a pigment concentrate is diluted in a white paint or white base, whether it is aqueous or solvent-based, it is also necessary to neutralize (that is to say to adjust the pH of) these pigment concentrates.
Typically, the pH of a latex is ideally adjusted to a value between 8 and 10, preferably between 8.5 and 9.5. This adjustment is preferably carried out using neutralizing amines (adjusting amines) added in an amount of 0.1 to 0.5% by weight relative to the weight of the paint to be neutralized. In pigment concentrates, the amount of neutralizer is, preferably, kept below 3.5% by weight.
The first neutralizers used were, for example, ammonium hydroxide or alkali metal hydroxides, especially sodium hydroxide.
Today, for reasons of volatility of the neutralizer or of water uptake by the paint films obtained, it is preferred to use other neutralizers, especially amines, and in particular 2-amino-2-methyl-1-propanol (CAS No. 124-68-5), sold under the brand AMP® at 90 or 95% in water under the names AMP® 90 and AMP® 95 respectively by Angus.
2-Amino-2-methyl-1-propanol thus has a good neutralizing action. However, pigment concentrates, latices and more generally paints neutralized with this product may exhibit instabilities during storage, with, in certain cases, the appearance of syneresis (phase separation with a liquid exudate at the surface), requiring a mechanical rehomogenization before use.
Moreover, it has been observed that paint films, especially those comprising latices and pigment concentrates neutralized with AMP®, are sensitive to humid atmospheres, and the films often display blistering phenomena under these conditions, which often makes the second application of a coat of paint difficult.
Furthermore, with a boiling point of around 165° C., this aminoalcohol is today considered to be a volatile organic compound, with regard to current legislation, especially in Europe.
Indeed, the regulations in force today impose the use, in paints, latices and generally in any type of curable film-forming coating, of compounds referred to as “non-VOC” compounds, that is to say that do not comprise or comprise very few volatile organic compounds.
However, the non-VOC neutralizers which are studied today have not proved very suitable for the specifications of paints. Thus, for example, the persistence of these neutralizers in the films often causes an unacceptable plasticization of the paints.
This is why it is necessary to research alternatives to the neutralizing agents used today, which make it possible to overcome the drawbacks mentioned above, while meeting the requirements of current regulations.
Thus, a first objective of the invention is to propose a neutralizing agent, especially for aqueous or solvent-based paints or for pigment concentrates for the preparation of said paints.
Another objective of the present invention is to propose a non-VOC neutralizing agent, especially for aqueous or solvent-based paints or for pigment concentrates for the preparation of said paints.
According to yet another objective, the present invention proposes a non-VOC neutralizing agent that enables good storage stability of aqueous or solvent-based paints or pigment concentrates.
Other objectives will appear in the description of the invention which follows.
These objectives are partly or completely achieved owing to the research work carried out by the applicant company.